Cleanup in settings

[maarcingebala]

This PR removes unused settings and environment variables.

Impact

• New migrations
• New/Updated API fields or mutations
• Deprecated API fields or mutations
• Removed API types, fields, or mutations

Pull Request Checklist

• Privileged queries and mutations are guarded by proper permission checks
• Database queries are optimized and the number of queries is constant
• Database migration files are up to date
• The changes are tested
• GraphQL schema and type definitions are up to date
• Changes are mentioned in the changelog

[codecov]

Codecov Report

Merging #5420 into master will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #5420      +/-   ##
==========================================
+ Coverage   91.11%   91.13%   +0.01%     
==========================================
  Files         283      283              
  Lines       18331    18327       -4     
  Branches     1608     1607       -1     
==========================================
  Hits        16702    16702              
+ Misses       1200     1196       -4     
  Partials      429      429              

Impacted Files	Coverage Δ
saleor/demo/settings.py	0.00% <ø> (ø)
saleor/wsgi/__init__.py	0.00% <ø> (ø)
saleor/product/models.py	91.51% <100.00%> (+0.39%)	⬆️
saleor/core/utils/draftjs.py	30.00% <0.00%> (+10.00%)	⬆️

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[patrys]

Do we need to update the docs to reflect those?

[maarcingebala]

@patrys Yup I'm working on changes in saleor-docs as well, today or tomorrow I'll push some updates to the saleor-2.10 branch.